Hi ChrisAmon, hope you're well!
Can I just confirm that you are aware of the following: when a main cast actor does not appear in an episode, all you need to do is not mark the checkbox in the main cast section signifying their appearance? They should not be added as 'credit only' in guest cast section.
I've come across this a few times here and there in your edits for the older shows (and have corrected a lot of them), but I just wanted to make sure you were aware that adding a missing main cast actor into the guest cast 'credit only' section should not be done.
Many thanks for all your hard work. :)